Telefonaktiebolaget Lm Ericsson (publ)

Mathias Larsson

Charilaos Christopoulos

Magnus Jändel

Touradj Ebrahmi

Joel Ask&euml;l&ouml;f

Diego Santa Cruz

In a method and a system for retrieving images in a client-server system, images are stored as a set of independently decodable units (CU's) on the server. A client issues a series of requests for image information. Each request contain a request number, information on what image information the client wants to see next and information on what image information the client had received at the time when the request was issued. The server does not have to store any state information (e.g. previous requests). On receiving a request, the server sends a restart marker, a confirmation of the request number and incremental image information corresponding to the request. The use of the method and the system as described herein will result in that no decoding of the whole bit stream will be required in the server. This will save a lot of time at the sender side (server side), since it not needs to a full decoding of the stream.

Partial retrieval of images in the compressed domain

In a method and a device for partial encryption and progressive transmission of images, a first section of the image file is compressed at reduced quality without decryption, and a second section of the image file is encrypted. Users having access to appropriate decryption keywords can decrypt this second section. The first section together with the decrypted second section can then be viewed as a full quality image. The storage space required for storing the first and section together is essentially the same as the storage space required for storing the unencrypted full quality image. By using the method and device as described herein storage and bandwidth requirements for partially encrypted images is reduced. Furthermore, object based composition and processing of encrypted objects are facilitated, and ROIs can be encrypted. Also, the shape of a ROI can be encrypted and the original object can be decrypted and restored in the compressed domain.

Method and a device for encryption of images

In a method and a system for encoding and transmission of still images having at least one region of interest (ROI), the ROI coefficients of an image transformed into the frequency domain, preferably using a wavelet transform are encoded so that they are transmitted first and can be decoded by a receiver without transmission of the boundary of the ROI. In a preferred embodiment the coefficients belonging to the ROI are shifted so that the minimum ROI coefficient is larger than the largest background coefficient. A receiver can then perform an opposite procedure and thereby obtain the ROI. By specifying how much the coefficients need to be shifted in order to avoid sending shape information several advantages are achieved. Thus, it is possible to avoid sending shape information and to avoid shape encoding at encoder side. Furthermore, there is no need for a shape decoder at receiver side, and there is no need for the receiver to produce the ROI mask. Also, in another preferred embodiment, the shifting (or scaling operations) required at encoder and decoder are also avoided.

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Saltsjöbaden, Sweden

Mathias Larsson